A man who watched the horrific assassination attempt on Donald Trump revealed he warned Secret Service agents about a gunman on a nearby roof minutes before shots rang out. 

The stunned witness, Greg Smith who owns Brenckle's Farms & Greenhouses, told DailyMail.com he saw the would-be assassin climb onto the top of a building outside the event in Butler, Pennsylvania, and that he was bewildered by the lack of action from agents.

'I'm thinking to myself, "Why is Trump still speaking on this stage right now? Why is he still up there talking?" he told DailyMail.com

After the gunman opened fire he saw the Secret Service 'blow his head off,' the man said in a video captured by the BBC.

A Donald Trump supporter claimed he warned Secret Service agents about a man with a rifle on a nearby roof minutes before they opened fire

A Donald Trump supporter claimed he warned Secret Service agents about a man with a rifle on a nearby roof minutes before they opened fire 

Donald Trump is seen with his fist in the air under a Stars and Stripes flag after Saturday's shooting in Butler, Pennsylvania, where the president was injured, with the shooter and a bystander both killed

Donald Trump is seen with his fist in the air under a Stars and Stripes flag after Saturday's shooting in Butler, Pennsylvania, where the president was injured, with the shooter and a bystander both killed 

'I saw Secret Service blow his head off,' he said, and then ran to collect his wife and three kids and return to safety.

'At this point, I'm feeling, as I think about it more and more, it just feels like a huge security failure to me,' he told DailyMail.com.

'This isn't a big place, there's not a lot of buildings around here, why is everything not covered.'

He said he had spotted a guy crawling up on the roof of a building.

'I noticed there's a guy crawling up the roof of that building,' he continued to DailyMail.com. 'I'm like, 'that doesn't seem right.'

He said the man definitely did not look like Secret Service, wearing tan and grey clothes, and was not in uniform.

Spotted police officers running around the building, appearing to be looking for someone.

"I'm pointing at the roof, like, 'Hey man, there's a guy on the roof with a rifle.'

Agents then climbed onto the roof, where the gunman was and images from social media appeared to show a man lying lifeless. 

The witness, a Trump supporter, told the BBC how he had seen the shooter prepare to assassinate the former president.

Questioned why there was no one in the water tower that overlooks the whole property he replied: 'I don't like it man, I don't like what's going on, I don't like what it feels like, I really don't.' 

Other rally attendees also saw him on the roof for three or four minutes with no action taken by law enforcement, he said. 

He said: 'We noticed a guy crawling, you know army, bear crawling up the roof of the building 50ft away from us.

'So we are standing there pointing at the guy crawling up the roof, he had a rifle, we could clearly see he had a rifle.

Bystanders are seen in the aftermath of the shooting. The man in the blood-splattered white t-shirt is an ER physician who told CBS News that he tried to help a bystander killed in the shooting. The dead bystander was on the ground just behind the man in blood-stained white

Bystanders are seen in the aftermath of the shooting. The man in the blood-splattered white t-shirt is an ER physician who told CBS News that he tried to help a bystander killed in the shooting. The dead bystander was on the ground just behind the man in blood-stained white

An extraordinary photo shows Donald Trump on the ground at Butler Show Grounds in Pennsylvania Saturday after he was injured in a shooting that left two people dead

An extraordinary photo shows Donald Trump on the ground at Butler Show Grounds in Pennsylvania Saturday after he was injured in a shooting that left two people dead 

Donald Trump pumps his fist moments after being shot at a re-election rally in Butler, Pennsylvania, on Saturday evening

Donald Trump pumps his fist moments after being shot at a re-election rally in Butler, Pennsylvania, on Saturday evening 

Law enforcement snipers set up before the arrival of former president Trump at the rally

Law enforcement snipers set up before the arrival of former president Trump at the rally 

'We are pointing at him, the police are down there running around on the ground. We are like hey man there is guy on the roof with a rifle - and the police are like "hey what? you know", they didn't know what was going on.

'We are like we can see him right here on the roof he's crawling. The next thing you know, I am like why is Trump still speaking? Why have they not pulled him off the stage? 

'I'm standing there pointing at him for two-three minutes, the secret service is looking at us from the top of the barn - I'm pointing at that roof.'

When asked if he was certain if the shots came from the man on the roof, the Trump supporter replied: '100 per cent, 100 per cent.'

Moments later Secret Service agents could be heard shouting 'the shooter is down'.

The agency confirmed the incident is being investigated as an attempted assassination. 

This is the moment Trump was injured - reportedly by a piece of flying teleprompter shattered by the gunshots

This is the moment Trump was injured - reportedly by a piece of flying teleprompter shattered by the gunshots 

A wider shot shows Trump being surrounded by Secret Service agents on the stage while stunned supporters look on. Security officials could be heard screaming 'the shooter is down' in the moments after gunfire erupted

A wider shot shows Trump being surrounded by Secret Service agents on the stage while stunned supporters look on. Security officials could be heard screaming 'the shooter is down' in the moments after gunfire erupted 

A wider shot shows Trump being surrounded by Secret Service agents on the stage while stunned supporters look on. Security officials could be heard screaming 'the shooter is down' in the moments after gunfire erupted

A wider shot shows Trump being surrounded by Secret Service agents on the stage while stunned supporters look on. Security officials could be heard screaming 'the shooter is down' in the moments after gunfire erupted 

The witness said the Secret Service 'probably' could not see the shooter the shape of the roof would have blocked their line of sight. 

'But why is there not Secret Service on all of these roofs here?' the man asked.

'I mean this is not a big place.'

At least eight bullets were fired moments after Trump got up to speak, and the president was seen grabbing the side of his head as blood poured from his ear and screams from terrified onlookers rang out. His team says that he is 'fine.'

It has since been reported that Trump may have been struck by a piece of flying glass from a teleprompter shattered during the shooting.

The identities of the shooter and the dead bystander have not yet been confirmed. It is also unclear where the shooter opened fire from and what kind of weapon was used.

In an image that has already gone around the world, Trump was pictured repeatedly pumping his fist with blood dripping from his face while being surrounded by Secret Service agents.

Moments later, he was rushed away to safety. Trump's team said further updates on the former president's condition will follow soon.

The president is seen being pushed into a Secret Service SUV, his raised fist still in the air

The president is seen being pushed into a Secret Service SUV, his raised fist still in the air 

His son Donald Trump Jr has since shared a post of his bloodied father with his fist clenched on X, captioned: 'He'll never stop fighting to save America.'

A spokesman added that the GOP 2024 hopeful added that Trump 'thanks law enforcement and first responders for their quick action during this heinous act.'

The DA added that an attendee was also killed at the rally, which was being held in Butler, Pennsylvania, on Saturday afternoon.

Within seconds, Trump was put to the floor by several Secret Service agents to protect him from the shooter, as the press pool said 'residual bangs' were heard after Trump hit the floor.

Trump stood up shortly after and pumped his fist at the crowd, leading to chants of 'USA' and 'Make America Great Again.'

He appeared to mouth the word 'fight' to supporters at the same moment.

Moments before he appeared to be hit, Trump was using a graphic at the rally to speak about illegal immigration.

Secret service encircled Trump within seconds of the shots being fired, and the agency said in a statement that the former president is 'safe.'

'The Secret Service has implemented protective measures and the former President is safe. This is now an active Secret Service investigation and further information will be released when available,' the statement read.

The extent of Trump's injuries are not clear, although he appeared to want to show his supporters that he was okay moments after being shot.

President Biden said in a statement that American 'must unite as one nation' in response to the horrific scenes.

'I have been briefed on the shooting at Donald Trump’s rally in Pennsylvania. I’m grateful to hear that he’s safe and doing well,' the White House said in a statement.

'I’m praying for him and his family and for all those who were at the rally, as we await further information.'

In a press conference later in the evening, Biden described the incident as 'sick', and said there is 'no place in America for this kind of violence.'

Donald Trump is pictured with blood on his face moments after shots rang out at a rally in Butler, Pennsylvania, on Saturday

Donald Trump is pictured with blood on his face moments after shots rang out at a rally in Butler, Pennsylvania, on Saturday 

The site of the Trump rally in Butler County Show Grounds is pictured before Trump came on stage. The president spoke on the stage just below the hoisted American flag with a crowd standing behind him.

The site of the Trump rally in Butler County Show Grounds is pictured before Trump came on stage. The president spoke on the stage just below the hoisted American flag with a crowd standing behind him. 

A spokesperson for the ATF said agents from the bureau have been deployed to assist with the aftermath of the chaos.

Rep. Dan Meuser, R-Pa., was standing front row at the rally along with Reps. Mike Kelly and GOP Senate candidate Dave McCormick.

Meuser said he heard between eight to 10 shots ring out as screams rippled through the crowd, according to Fox News.

He added that it appeared there were multiple people in the crowd may have been impacted by the bullets and the local district attorney confirmed that at least one person is 'believed to be dead.'

Pennsylvania Governor Josh Shapiro condemned the shocking scenes in his state.

'Violence targeted at any political party or political leader is absolutely unacceptable,' Shapiro said on X.

'It has no place in Pennsylvania or the United States. I have been briefed on the situation. @PAStatePolice are on the scene in Butler County and working with our federal and local partners.'

An emergency room doctor at the Trump rally revealed how he performed CPR on a member of the crowd after the attempted assassination.

'I heard the shots. I thought it was firecrackers begin with. Somebody over there was screaming 'he's been shot he's been shot,'' said the man who had blood splattered all over his white USA shirt. 'So I made my way over. I said I'm an emergency department physician. Let me help you.'

'The guy had spun around was jammed between the benches and a head shot here. There's lots of blood and he had brain matter,' he told CBS News.